Why are you concerned about this?
Her situation not the general@-2?
Oh I see. If you're children love there then that is a reasonable concer. I wouldn't worry about her though. She is an adult. Of women choose to live with men who abuse them then that is a matter for them. It is dangerous to get involved with them because they always turn on you.
On your primary point though, there's nothing to stop you recording her. It does offend the DPA but that wouldn't stop it being used in a criminal case.
However, they won't prosecute on the basis of her claims on tape alone. That isn't enough to meet the charging standard.
You may be able to get an injunction from the family court although I don't do family.